Radio receiving apparatus



Nov. 6 1923. 1,473,417

F. G. BEETEM RADIO RECEIVING APPARATUS Filed June 16. 1920 entornos,

Patented Nov.. 6, 1923..

FRANK G. BEETH, F PHILADELPHIA, PENNSYLVAN1A RADIO RECEIVING APPARATUS.

Application led J'une 16, 1920. Serial No. 889,442.

To all whom it may oon-cern:

Be it known that I, FRANK G. BEETEM, a citizen of the United States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Radio Receiving Apparatus, of which the *following is a specification.

This invention relates to radio receiving systems embodying 'audions or vacuum tubes.

One of the objects of my invention is to provide a suitable regulating device for the filament circuit of an audion or vacuum tube, so arranged With adjustable handi operated resistances that any given setting for the filament excitation may be obtained and afterward the filament current vand voltage will remain substantially constant, irrespective of normal changes in the volt age of the battery or other source supplying this filament circuit.

Itis a well known fact that the voltage of primary or secondary batteries varies throughout the discharge of' the battery. Starting at a given point the tendency is for the Voltage to decrease more or less steadily with time during the period when current is being drawn from the battery. With some forms or types of batteries this voltage regulation is very poor and so in the case of the filament circuit of audion or vacuum tubes, compensation for the decrease of voltage of the battery exciting the fiiament is made from time to time with adjustable resistances in series with the filament in the battery circuit, the amount o resistance included in the filament circuit being varied by manual adjustment to maintain constant current.

in some types of radio receiving apparatus, and especially with batteries having poor voltage characteristics, the necessity for constant adjustment is exceedingly objectionable and frequently results in the loss of signals or portions thereof, which under the conditions of a constant filament current would not occur.

A particular object of my invention is to render it possible to use an type of battery, at least for a considerab e period, witl1- out the neeessit for constant adjustment. To accomplish t is, propose to include in the .filament circuit a device which will, within the limits' ot its particular design,

automatically maintain a constant filamentcurrent and consequently a constant filament temperature.

Further, the invention has for an object the provision of suitable means for simplifying the control of audions or vacuum tubes in the reception of oscillations of definite radio frequency by providing automatic means for maintaining constant current in the filament circuit of the audion in combina-tion with manual means for making the initial adjustment whereby the auto'- matic means is operated at its point of maximum effectiveness and at the same time the current in the filament is adjusted to the desired value, and is thereafter maintained at said value automatically and without tur ther manual adjustment, notwithstanding variations in the voltage of the source of current.

Further features and objects of m invention will be more fully understood rom the following detailed description and the accompanying drawing, in which:

Figure 1 is a diagrammatic view of the application of my invention to a form of radio receiving circuit.

Figure 2 is a diagram showing one relation or current and voltage of an iron Wire ballast.

Referring to Fig. 1, the antenna 1, grounded at 2, is suitably connected to the closed, tuned circuit of the receiving apparatus as by means of the coil` 3 inductively arranged with the reactance coil 4 of the closed tuned circuit. The capacity of the antenna circuit is adjusted by the variable condenser 3a. The condensance of the closed tuned circuit is provided by the variable condenser 5, connected by the leads 6, 7, with the respective leads 8, 9, of the inductance coil 4.

One lead of the condenser 5, say the lead 6, is connected to the conductor 10, through the condenser 11 and to the grid 120i the audion or vacuum tube 13, whereas the other lead 7 of the condenser 5 is connected by the conductor let to `oneterrninal 15 of the filament 16 of the audion or vacuum' tube'13.

The plate or anode 17 is connected by the conductor 18 to one terminal of the head telephone 19, or other suitable aural indi. eating device, the other terminal of such indicating device 19 being connected by the conductor 20 to one terminal of a battery 21, such as a storage battery, through such battery 21, thence through the conductor 22, conductor 23 and to the terminal 15 of the` filament 16.

Between the said terminal 15 of the iilament 16 of the audion or vacuum tube 13, and its other terminal 24, I arrange the means for maintaining the current value of the electric current supplied by the battery 25 to the ilament 16 substantially constant, notwithstanding variations in electroniotive force or potential of the battery 25.

As one form of such means I have shown, as indicated in Fig. 1, the iron Wire ballast 26, one terminal 27 being connected by the lead 28 through the storage battery 25 to the lead 29, connected by the conductor 23 to the terminal 15 of the filament 16. the other terminal 30 ol the iron lWire ballast 26 being connected by the lead 3l through the variable ohmic resistance 32 and the conductor 33 to the terminal 24 ot the filament 16.

In some forms of apparatus I may connect between the filament terminals 15 and 24, a variable ohmiciresistance, 34, of zero or slightly negative temperature coefcient material, which may be used to rdivert a part of the current furnished by the battery 25, so that the Whole current in lead 33 does not pass through the lilament 16. NOW for any adjustment of resistance 34 the filament current ivill remainpractically constant at the adjusted value since the current in lead 33 is maintained substantially constant by the action of the ballast 26. Upon tuning the closed circuit the resistance 32 is adjusted so that the maximum normal drop of poten` tial across the ballast 26, as indicated by the curve shown in Fig. 2, is obtained and at the same time resistance 34 is adjusted for the beat-tone indicated by the head telephone. Of course the system is workable Without the resistances 32 or 34, for any particular set of conditions but the addition of these resistances simplifies the problem of iron wire ballast manufacture. The addition of the resistance 34 also improves the regulation of the lilament current.- A larger ballast is requiredvwhen this resistance 34 is used.

Upon tuning the closed circuit including the inductance coil 4 and condenserr5 to the frequency desired to be received, the ohmic resistance A34 is adjusted for the beat-tone indicated by the head telephone as desired by the operator. Assuming that the electromo` tive force or potential of the battery 25 has any certainv value at the instant of such adjustment as is indicated by the` ordinate 40, on the coordinate axes of current and electromotive force values indicated in Fig. 2, the ensuing drop in potential of the battery takes place Without substantially altering the current value. Thecurrent-electrometive force curve plotted to right-angled co-' ordinate axes includes a curve portion 41 located between the point 42 and the point 43 which is substant-ially parallel to the abscissa axis, as indicated in Fig. 2; in other Words, the current values represented by the ordinates 44, 45, at the eXtreme limits of such curved portion 4l, are substantially equal, and such curve portion 41 is substantially a straight line between such point 42 and such point v43.

By reason of my invention, upon obtaining the initial adjustment of the receiving apparatus', such initial adjustment need not be disturbed notwithstanding variations in potential of the source of electric energy energizing the filament of the audion or vacuum tube.

In order to more clearly explain the operation of the several elements of the combination described above, the following numerical examples are given Assume the charateristics ot the iron wire ballast are such that the coordinates of point 43 in Fig. 2 correspond to 2.00 amperes (ordinate) and 1.5 volts (abscissa) and the coordinates of point 42 correspond-to 1.98 amperes (ordinate) and 1.0 volt (abscis'sa). To secure the most effective automatic con trol, the iron Wire ballast should be operated between these limits. Assume, further, that for some desired adjustment of the reception circuit the lament should carry 1.5 amperes and when carrying this current, the voltage across its terminals is 3.6 volts. Assume ali so that the initial voltage of the batteryv 25 is 6.0 volts, but that this may volts as it discharges.' In order that the iron Wire ballast may carry 2.00 amperes, and the filament may at the same time car 1.50 amperes, the resistance 34 should be adlusted to divert 0.5 ampere at 3.6 volt-sri. e., 1t should have a value of 7.2 ohms. Then the sum of the'voltage across the filament (3.6 volts) and the desired voltage across the iron Wire ballast` (1.5 volts) is 5.1 volts. Since the initial battery volta is 6.0 volts, the difference between this anA 5.1 volts (0.9 volts) must be absorbed b the resistance 32 when carrying the tota current of 2.0 amperes. Therefore, resistance 32 must be adjusted to a value of 0.45 ohm. Now if the battery voltage drops to v5.5 volts, the :totaldrop to 5.5 l

current, by reason of the automatic action of the iron wire ballast, will not fall below 1.98 amperes, though the voltage across this ballast may drop from 1.5 volts to 1.0, thus compensatin for the drop in battery voltage, While maintaining the total currentl and therefore the current in the lilament constant.

Now suppose for some other adjustment of the reception circuit it is desired to maintain only 1.0 ampere in the filament, at which current value the voltage across its terminal is say 3.0 volts. maximum electiveness of the iron Wire-v ballast, the total current should still be 2.0

In order to maintain the I be 3.0 ohms. The total drop amperes. The adjustment of resistance 34 should' therefore be such as to divert 1.0 ampere at 3.0 volts,-i. e., its value should across the lilament (13.0 volts) and the' iron Wire ballast (initia ly 1.5 volts) will thenbe' 4.5 volts, and the initial battery voltage being 6.0 volts, it is necessary to adjust the resistance 32 to give a drop of 1.5 when carrying 2.0 amperes, i. e., its value should be 0.75 ohms. If now, the batte voltage drops from 6.0 volts to 5.5A volts, t e voltage across the iron Wire ballast will drop from 1.5 volts to 1.0

volts as before, while maintaining'the current constant. V

The above .examples will clearly explain how with the combination disclosed the lilament current may be manually ad'usted at any desired value within the limits or which the apparatus is designed and thereafter.

automatically Amaintained at said value throughout wide variations inthe voltage of the source, and these results are obtained Without any change inthe design of the iron Wire ballast. In other words, the same iron wire ballast, though designed to maintain a constant current of 2.00 amperes may be used to control a current of either 1.5 or 1.0 or in fact any other current not exceeding 2.0 amperes in the filament. y

Whereas I have described my invention by reference to specic forms thereof, it will be understood that many changes and modifications may be made without departing from the spirit of the invention, as defined by the appended claims.

What I claim is: 1. In combination, the lament of an audion or vacuum tube, a source of current therefor, a resistor of hi h positive temperabetween the sourcev ture coefficient connec and the filament and adapted to maintain a substantially constant current flow, anda resistor connected in parallel with the filament to divert a portion of said current whereby the current in the lament is maintained constant'at a different value from that of the current from the source.

2. In combination, the filament of an audion or vacuum tube, a source of current therefor, an iron Wirey ballast connected betweenv the source and the lainent and adapted to maintain a substantiallyl oonstant flow of current within a certain range of impressed voltage, a resistor connected in series with said ballast and adapted to adjust said impressed voltage within the desired range, and a resistor connected in parallel with the filament whereby the current in said filament is maintained substantially constant at a value diferent from that through the iron wire'` ballast. j I j 3.` In combination, the lament of an audion or 'vacuum tube, a source of current therefor, an iron Wire ballast connected between A. the source `and the filament and adapted to maintain aA substantially constant How of current Within a certain range of impressed voltage, an adjustable resistor connected in series with said ballast and adapted to adjust said impressed volta e Within the desired range and an adjustab e f resistor connected inlparallel `Withvthe' filament for adjusting t constant current which flows through the filament. v

In testimony whereof I alix m signature. FRANK Gr.I Bll'jETEfM.

e proportion of said. 

